Bar and plate air-oil heat exchanger

ABSTRACT

An air-oil heat exchanger used in a compression system that includes a compressor is disclosed. The heat exchanger can be used to cool oil in one embodiment which is used in a compression process. The heat exchanger can be a bar-and-plate type heat exchanger having a number of external fins, internal fins, parting sheets, and header bars. The external fins can include louvers formed therein. An arrangement of multiple unrelated components can be provided that improves pressure loss and reduces weight.

TECHNICAL FIELD

The present invention generally relates to compression system heatexchangers, and more particularly, but not exclusively, to particulararrangement of bar and plate heat exchanger.

BACKGROUND

Providing improvements in bar and plate heat exchangers used incompression systems remains an area of interest. Some existing systemshave various shortcomings relative to certain applications. Accordingly,there remains a need for further contributions in this area oftechnology.

SUMMARY

One embodiment of the present invention is a unique heat exchanger foruse with a compression system. Other embodiments include apparatuses,systems, devices, hardware, methods, and combinations for reducedpressure loss and low weight heat exchangers. Further embodiments,forms, features, aspects, benefits, and advantages of the presentapplication shall become apparent from the description and figuresprovided herewith.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts a schematic of a compression system having an air-oilheat exchanger.

FIG. 2 depicts a prior art example of a bar and plate heat exchanger.

FIG. 3 depicts an embodiment of an external fin.

FIG. 4 depicts an embodiment of an external fin.

FIG. 5 depicts an embodiment of an internal fin.

FIG. 6 depicts an alternative embodiment to that shown in FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any alterations and further modificationsin the described embodiments, and any further applications of theprinciples of the invention as described herein are contemplated aswould normally occur to one skilled in the art to which the inventionrelates.

With reference to FIG. 1, a compressor system 50 is disclosed having acompressor 52 and oil cooler 54. Although only the compressor 52 and oilcooler 54 is depicted, other components may also be included in anygiven embodiment of the compressor system 50, including, but not limitedto, a compressor dryer, oil sump, etc. The compressor dryer can be arefrigerated dryer or a desiccant based dryer, among potential others.The compressor 52 is used to compress a compressible fluid 56, such asair, and deliver a compressed air 58 to an end user, customer,reservoir, or other suitable destination. The compressor 52 can take ona variety of forms. For example, in one non-limiting embodiment thecompressor 52 is an oil filled screw compressor, but other forms arealso contemplated herein.

The oil cooler 54 is used to cool oil or other fluid used in conjunctionwith operation of the compressor 52. The oil, or other suitable fluid,can be used for lubrication and cooling purposes within the compressor52, among other uses. The oil cooler 52 can structured as an air-oilheat exchanger and in the illustrated embodiment includes a fan 60 orother suitable fluid moving devices which provides a stream of movingair useful in exchanging heat with oil routed through the oil cooler 54.

Yet another embodiment is shown in FIG. 6 of a compressor system 50 thatincludes additional components such as a motor 76, separator tank 78,combined air cooler 80 and oil cooler 54 (in which the coolers areconnected and cooled by a common fan), combi block with thermal valve82, and oil filter 84. The route of mixed oil/air, separated oil andair, as well as the hot and cold sides of oil and air should be readilyapparent from the figure.

A prior art embodiment of an oil cooler is shown in FIG. 2. Shown in theillustration is a cutaway view of a bar and plate type of heat exchanger54. The heat exchanger 54 includes a number of external fins 62,internal fins 64, a side bracket 66, parting sheets 68, and header bar70. In general, the bar and plate heat exchanger 54 shown in FIG. 2includes a stack of alternating flat plates (e.g. the parting sheets 68)and fins (e.g. the internal fins 64 and external fins 62) that arebrazed together to form a single solid unit, though other manufacturingtechniques may also be used. Though only a limited number of each ofthese components are illustrated in FIG. 2, it will be understood thatother numbers of components can also be present. To set forth just onenon-limiting example, although the header bars 70 are shown on only onelateral side of the heat exchanger 54, the other side of the heatexchanger 54 can also include additional header bars 70.

The external fins 62 can be formed of any heat conductive material, andcan be triangular shaped as illustrated in FIG. 2. Such materials thatthe external fins 62 can be made out of include metal, which may bealuminum or aluminum alloy in many embodiments, but other metals and/ormetal alloys are also contemplated herein. The external fins 62 can bedescribed as fin members that are shaped in a triangular pattern thatalternatingly extends between parting sheets located on either side ofthe external fins 62. Each of the fin members can include a plurality oflouvers (described further below) formed as openings with an angled hoodor vent which is useful to direct a passing fluid such as cooling air.The plurality of louvers can be assembled in small groupings that aredistributed along the length of the external fins 62, as can be seen bythe groupings illustrated in FIG. 2.

FIG. 3 depicts one embodiment of the louvers 72. The louvers 72 can beset at a louver angle θ which is an acute angle formed between thelouver 72 and surface of the external fin 62. The acute angle θ of thelouvers 72 can all be oriented in the same direction along the length ofthe external fins 62 and on the same side of the fins 62, but in someembodiments other variations are possible. For example, in someembodiments the louvers 72 can be formed with an acute angle pointing ina direction against a flow of cooling air over a first half of thelength of the external fins 62, while the second half of the length ofthe external fins 62 can have louvers pointing in an equivalent acuteangle but oriented in a direction along the flow of cooling air. Thelouvers 72 can also have a louver pitch L_(p) which can be described asthe distance between the tips of the louvers measured along thedirection of the fin 62.

FIG. 4 depicts some geometric details of the external fins 62. Theexternal fins 62 can have individual fins 74 which are distributed alongthe length of the external fins 62. The number of individual fins 74 canbe counted over a given length and a quantification can be made of thefrequency of fins. For example, the number of fins per inch can becounted and a “fin per inch” quantity can be used to describe thedensity of individual fins 74 over the length of the external fins 62.The F_(h) or fin height shown in FIG. 4 is the height of the fins 62 asthey reach between adjacent walls (e.g. the parting sheets 68).

Turning now to FIG. 5, certain geometric details of the internal fins 64are illustrated. The internal fins 64 can be of the offset strip fintype having a length λ, height h, and pitch s. The height of theinternal fins 64 can be described as the open space between partingsheets 68 less the material thickness of the sheet that makes up theinternal fins 64. The pitch can be the open space within the internalfins 64 between upright wall sections of the fins 64.

The external fins 62 and/or the internal fins 64 can be made using avariety of approaches, which include forming a unitary member, couplingseparate components together to form the member, etc. To set forth justa few examples, the external fins 62 can be stamped into shape to formthe triangular shape as depicted in the illustrated embodiment. Theoffset strip type of the internal fins 64 as illustrated can include anumber of separate strips that are individually stamped, which are thenbrought together in an offset configuration before being consolidatedinto an internal fin construction.

It will be appreciated that in highly complex, multi-variate systems, itis not always clear which combination of parameters provide forimprovements. The instant application has discovered heretoforeunappreciated arrangement of multiple and unrelated components in theheat exchanger 54 which unexpectedly provided for an appreciable degreein reduced pressure loss and weight. Prior to their discovery asdisclosed in the instant application, it was unknown which combinationand degree of factors in the aggregate provided the best solution. As aresult of the inventive concepts described herein, it was discoveredthat at least one potential candidate, internal strip length, was deemedto either not impact the overall study or minimally impact the study,while other parameters were changed quite significantly from theconventional baseline indicating that the state of the art was unawareof the combination and degree of changes required to provide a bettersolution.

The combination of parameters that have led to unexpected improvementsare as follows (listing the known baseline prior system for comparison):

Option 1 Low air side Option 2 Parameter Baseline pr. Drop Low weightExternal FIN HEIGHT 0.375 0.438 0.488 Internal FIN HEIGHT 0.125 0.0980.100 Internal FIN PITCH 0.074 0.069 0.081 External FIN PER INCH 12 1112 Internal strip length 0.14 0.14 0.14 External LOUVER ANGLE 23.0 25.223.5 External LOUVER PITCH 0.045 0.035 0.035 Output Air side pr. Drop(Pa) 493.7 386.5 430.7 Heat transfer (W) 251317 253002 252603 Oil outlettemperature 76.0 75.8 75.9 (deg C.) Coil weight (Kg) 105.0 89.6 85.9 Oilside pr. Drop (Pa) 38895 56993 50198

The dimensions quoted herein regarding various geometries of the heatexchanger need not always be precisely exact as is well understood.Manufacturing tolerances permit some degree of dimensional variation.

Of the parameters listed above, the first four listed in the chart(external fin height, internal fin height, internal fin pitch, andexternal fin per inch) where surprisingly found to be most important inachieving the desired objectives, while the remaining parameters(internal strip length, external louver angle, and external louverpitch) were deemed to be less important.

The arrangement of components as described above was determined assumingthat a core face area of 15.39 square feet, core depth of 6 inches,blower air flow of 14,145 cubic feet per minute, air inlet temperatureof 120 degrees F., oil inlet temperature of 212 degrees F., and an oilflow rate of 42,900 lb/hr.

It is possible to construct a heat exchanger using values that arebetween the numbers listed above in Option 1 and Option 2, which willprovide for a tradeoff between low pressure loss and low weight.

The oil cooler 54 embodiments disclosed herein could be used for anair-to-air heat exchanger as well, such as might be used in interstagecooling of a multi-stage compressor system, or as an aftercooler inother embodiments, to set forth just a few non-limiting examples.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiments have been shown and described and thatall changes and modifications that come within the spirit of theinventions are desired to be protected. It should be understood thatwhile the use of words such as preferable, preferably, preferred or morepreferred utilized in the description above indicate that the feature sodescribed may be more desirable, it nonetheless may not be necessary andembodiments lacking the same may be contemplated as within the scope ofthe invention, the scope being defined by the claims that follow. Inreading the claims, it is intended that when words such as “a,” “an,”“at least one,” or “at least one portion” are used there is no intentionto limit the claim to only one item unless specifically stated to thecontrary in the claim. When the language “at least a portion” and/or “aportion” is used the item can include a portion and/or the entire itemunless specifically stated to the contrary.

Unless specified or limited otherwise, the terms “mounted,” “connected,”“supported,” and “coupled” and variations thereof are used broadly andencompass both direct and indirect mountings, connections, supports, andcouplings. Further, “connected” and “coupled” are not restricted tophysical or mechanical connections or couplings.

What is claimed is:
 1. An apparatus comprising: a bar and plate heatexchanger having an arrangement of external fins disposed in a firstflow path separated from an arrangement of internal fins disposed in asecond flow path by a parting sheet, the first flow path distinct fromthe second flow path, wherein the arrangement of external fins and thearrangement of internal fins are structured according to the following:external fin height of about 0.438″; internal fin height of about0.098″; internal fin pitch of about 0.069″; and external fin per inch ofabout
 11. 2. The apparatus of claim 1, wherein the second flow pathwithin which the internal fins are disposed is structured to containoil.
 3. The apparatus of claim 2, which further includes a compressorand an oil sump, the second flow path including a passage to convey oilbetween the oil sump and the internal fins.
 4. The apparatus of claim 3,which further includes another arrangement of external fins, thearrangement of internal fins disposed between the arrangement ofexternal fins and the another arrangement of external fins, whichfurther includes another parting sheet between the internal fins and theanother arrangement of external fins, and wherein internal strip lengthis about 0.14″.
 5. The apparatus of claim 4, which further includesanother arrangement of internal fins structured to flow oil and in fluidcommunication with the oil sump, and wherein the external fins includesa plurality of groupings of louvers defined by the external louverangle.
 6. The apparatus of claim 5, which further includes a header bardisposed at an end of the arrangement of external fins, and wherein atleast one of the plurality of groupings of louvers is oriented in adirection that opposes a direction of at least another one of theplurality of groupings of louvers.
 7. The apparatus of claim 1, whereinthe first flow path is constructed to convey a flow of air and isoriented transverse to the second flow path, and wherein the arrangementof internal fins further include an external louver angle of about 25.2degrees, and an external louver pitch of about 0.035″, and wherein thearrangement of internal fins are offset strip fins.
 8. An apparatuscomprising: a compressor system heat exchanger having a first externalfin construction fluidly separated from a first internal finconstruction by a parting sheet, wherein the arrangement of externalfins and the arrangement of internal fins are structured according tothe following: external fin height of about 0.488″; internal fin heightof about 0.1″; and internal fin pitch of about 0.081″.
 9. The apparatusof claim 8, wherein the heat exchanger is an air/oil heat exchanger,with the first internal fin is structured to flow oil in a flow paththat includes an oil sump.
 10. The apparatus of claim 9, wherein thecompressor system includes a rotatable compressor element structured topressurize a flow of air, and wherein the first external fin isstructured to flow air in a flow path for the air/oil heat exchanger.11. The apparatus of claim 10, wherein the compressor system includes asecond and third external fin construction, wherein the first, second,and third external fin construction are each a single unitary fin memberconstructed to be disposed within a fluid oil flow path, whereinexternal fin per inch is 12, and internal strip length is 0.14″.
 12. Theapparatus of claim 11, which further includes a header bar disposed ateach end of the first, second, and third external fin construction, andwhich further includes a second and third internal fin construction. 13.The apparatus of claim 12, which further includes a plurality of partingsheets, each neighboring pair of external fin constructions and internalfin constructions having a parting sheet disposed therebetween.
 14. Theapparatus of claim 13, wherein each of the first, second, and thirdexternal fin constructions include a plurality of groupings of louvers.15. The apparatus of claim 8, wherein the internal fin constructions areoffset strip fins, and wherein the first flow path is transverse to thesecond flow path, and wherein the arrangement of external fins and thearrangement of internal fins are further structured according to: anexternal louver angle of about 23.5 degrees; and an external louverpitch of about 0.035″.
 16. An apparatus comprising: a heat exchanger ofthe bar and plate type for use with an air compressor system includes anplurality of external fins and a plurality of internal fins, and aparting plate disposed between the external fin device and the internalfin device, the parting plate separating a first flow path in which theexternal fin device is disposed and a second flow path in which theinternal fin device is disposed, the external fin device and theinternal fin device having an arrangement as follows: external finheight between about 0.438″ and about 0.488″; internal fin heightbetween about 0.098″ and about 0.100″; internal fin pitch between about0.069″ and about 0.081″; external fin per inch of between 11 and 12; andinternal strip length of about 0.14″.
 17. The apparatus of claim 16,wherein the first flow path is transverse to the second flow path, thefirst flow path is an air flow path, and the second flow path is an oilflow path.
 18. The apparatus of claim 17, which further includes an oilsump in fluid communication with the second flow path.
 19. The apparatusof claim 18, wherein the plurality of internal fins includes a first setof internal fins offset and separate from a second set of internal fins,wherein the plurality of external fins includes a first set of externalfins offset and separate from a second set of external fins, the heatexchanger having an alternating stacked pattern which includes the firstset of internal fins, then the first set of external fins, then thesecond set of internal fins, then the second set of external fins. 20.The apparatus of claim 19, wherein the plurality of internal fins areoffset strip fins, which further includes a header bar disposed at theend of each of the first and second set of external fins, and whereinthe first set of external fins has separate groupings of louvers; andwherein the external fin device and the internal fin device having afurther arrangement of: an external louver angle between about 23.5degrees and about 25.2 degrees, and an external louver pitch of about0.035″.